The invention relates to an electric machine comprising a rotor and a stator having a horizontal peripheral direction, wherein the rotor and stator interact electromagnetically, wherein the stator has a number of offset, radially oriented teeth for a winding, wherein the teeth are arranged in the horizontal peripheral direction, wherein the teeth are each connected to a tooth cap and to a tooth pole. Furthermore, the invention further relates to a method for operating such an electric machine and to a production method for such an electric machine.
Armatures of electric machines are frequently equipped with windings on teeth, which are interconnected in a tooth on the end face of a laminated core. The higher the load on the electric machine, the more the tooth, as well as the winding around a tooth itself, heats up. This also applies in particular for electric motors with high rotational speeds. At high rotational speeds, armature tooth caps are frequently required, particularly for radially bracing the teeth that are subject to centrifugal force. Said tooth caps generally consist of high-strength steel and are implemented as closed structures. The tooth cap is shrunk onto a bolt of a shaft on the one axial side. The bolt frequently possesses radially aligned ventilation holes, if the electric motor is designed for higher outputs. The tooth cap, conversely, is embodied in a closed manner for stability reasons. Especially in the cap region on the winding, this leads to an insufficient dissipation of the waste heat arising there. Zones arise with very high winding temperatures (so-called “hotspots”).
For this reason, the teeth are cast or impregnated in order to improve the heat dissipation from the tooth, inter alia. By casting and impregnating the teeth, a fixing of the windings may also be effected. Thus, in addition to the mechanical fixing and compacting of the laminated core, an electrical insulation of the windings from one another is achieved. The casting compound or the impregnating resin cannot, however, flow around the tooth completely. This means that the optimal heat dissipation and thus the optimal performance of the motor cannot be achieved.
After the winding has been impregnated into the grooves and the tooth, the tooth forms a solid, resin-filled unit, through which no cooling air can pass. In teeth of this kind, regular heat sources therefore emerge which restrict the thermal utilization of the dynamoelectric machine.
A high winding temperature therefore diminishes the service life of the winding insulation by a considerable amount. As a countermeasure, the output of the machine is therefore usually restricted or the machine is designed to be thermally overdimensioned.